The present invention relates generally to the field of battery saving controllers for portable communication receivers, and more particularly to an adaptive battery saving controller suitable for use with portable communication receivers utilizing synchronous signaling protocols.
Battery saving circuits for controlling battery power consumption have been utilized in battery powered communication receivers, such as battery powered paging receivers, for many years. The battery saving controllers were provided to conserve battery power and to extend the useable life of the batteries. The specific operation of such battery saving controllers was largely determined by the type of signaling format used within the paging system in which the battery powered paging receiver was operated. The battery saving operation for a typical prior art battery saving controller is shown in FIG. 1, which represents the battery saving operation for one of the well known synchronous signaling formats, the POCSAG signaling format. As shown in FIG. 1, the POCSAG signaling format provides a thirty-two bit address code word 102 and a thirty-two bit message code word 104 for numeric and alphanumeric message transmission. In the POCSAG signaling format, the address code word is distinguished from the message code word by the value of the first data bit, B0. Address code words are identified by a logical zero bit value for the first data bit, whereas message code words are identified by a logical one bit value for the first data bit. Message transmissions 105 in the POCSAG signaling format begin with the transmission of a preamble code word 106 followed by one or more POCSAG batches 108. Each POCSAG batch 108, comprises a synchronization code word 110, followed by eight transmission frames 112, each frame providing for the transmission of two address code words, an address code word and a message code word, two message code words, or idle code word when address or message code words are not being transmitted. Individual pagers operating within the system are assigned to one of the eight transmission frames to effect the well known POCSAG battery saving operation. The battery saving operation of the prior art POCSAG battery saving controller is shown by the battery saving strobe waveform 114, which depicts supplying power to at least the receiver portion of the paging receiver during the transmission frame to which the paging receiver was assigned. In the example shown, the paging receiver was assigned to frame 5. When the paging receiver was initially turned on, or when the paging receiver was searching for a POCSAG signal, power was periodically provided to the receiver portion of the paging receiver for a predetermined time period sufficient for the paging receiver to detect the transmission of a preamble signal. When the preamble signal was not detected within the predetermined time period, the supply of power to the receiver portion was suspended, until the next predetermined time interval. As shown in FIG. 1, the preamble signal was detected by the paging receiver during the time period 116 during which power was supplied to the receiver portion. During this time period the receiver obtained bit synchronization with the preamble signal and thereafter obtained word synchronization with the synchronization code word 110. Power to the receiver portion was then suspended until the assigned frame time interval. Power was again supplied to the receiver portion at a time 122 prior to the assigned frame to enable the receiver operation to stabilize, thereafter allowing the transmitted address and message information to be received and processed during the assigned frame time interval 118. Power to the receiver portion was again suspended at the end of the assigned frame time interval 118, in the event no message was intended for the paging receiver, until the next transmission of the synchronization code word during the synchronization code word time interval 120. Thereafter, power was regularly supplied to the receiver during the assigned frame time interval and during the synchronization code word time interval. Such a battery saving operation as utilized by the prior art battery saving controllers, while providing a significant improvement in battery life, resulted in a significant amount of information which was received and processed, even when this information was not intended for the paging receiver. This was especially true in paging systems transmitting numeric and alphanumeric messages, as power was maintained to the receiver portion during the entire assigned frame time interval, even in those instances when the address and corresponding message information which was received was not intended for the paging receiver.